Systems and methods for operating a compression system

ABSTRACT

A method of operating a compression system includes determining, by a controller, at least one of an operational point distance to surge and a surge margin based upon at least one of an electrical power consumed by a compressor and an electrical current consumed by the compressor, and at least one thermodynamic state measurement associated with the compressor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 62/431,959 filed Dec. 9, 2016, which is hereby incorporated by reference in its entirety.

BACKGROUND

The subject matter disclosed herein relates to a compression system, and more particularly to systems and methods of operating a compression system.

As compressors operate, performance of the compressor and associated processes and equipment may be affected by disruptive events in the compressor and/or interaction between performance of the compressor and other elements of the system. Such disruptive events may include surge, incipient surge, and rotating stall events in the compression system. For example, surge can be described as large and self-sustaining pressure and flow oscillations in the compression system, resulting from the interaction between the characteristics of the compressor and surrounding equipment including piping, vessels, valves, coolers, and/or any other equipment that may affect the pressure, temperature, gas composition, and/or flow in the compressor.

Other compressor parameters, such as rotating speed, consumed power and/or motor current may also be affected, because pressure and flow oscillations can result in changes in the power consumed by the compressor. Surge may occur as the flow through the compressor is reduced to a point where flow distortions can appear around the rotating and non-rotating components of the compressor, due to boundary layer separation, part or all of the flow between, for example, two adjacent compressor stages is blocked. Surge may result in significant pressure-flow pulsations and may lead to flow reversal through the compressor.

Thus, surge events can be disruptive, in some cases extremely disruptive, to any process or equipment, such as a compression system, for example, a refining or a chemical process, or turbine engine driving a generator in a power plant.

BRIEF DESCRIPTION

In one aspect, a method of operating a compression system is provided. The method includes determining, by an antisurge controller, at least one of an operational point distance to surge and a surge margin based upon at least one of an electrical power consumed by a compressor and an electrical current consumed by the compressor, and at least one thermodynamic state measurement associated with the compressor.

In another aspect, a compression system is provided. The compression system includes a compressor including an inlet, and an antisurge controller coupled to the compressor. The antisurge controller is configured to determine at least one of an operational point distance to surge and a surge margin based upon at least one of an electrical power consumed by the compressor and an electrical current consumed by the compressor, and at least one thermodynamic state measurement associated with the compressor.

In yet another aspect, an article of manufacture is provided. The article of manufacture includes a non-transitory, tangible, computer readable storage medium having instructions stored thereon that, in response to execution by an antisurge controller, cause the antisurge controller to perform operations including determining, by the antisurge controller, at least one of an operational point distance to surge and a surge margin based upon at least one of an electrical power consumed by a compressor and an electrical current consumed by the compressor, and at least one thermodynamic state measurement associated with the compressor.

DRAWINGS

These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a block diagram of an exemplary compression system;

FIG. 2 is an exemplary compressor map of the compression system shown in FIG. 1;

FIG. 3 is a block diagram of an exemplary control system that may be used with compression system shown at FIG. 1, in which control operations performed by the control system are illustrated;

FIG. 4 is a flowchart illustrating an exemplary process for use in determining an operational point distance to surge for the compression system shown at FIG. 1;

FIG. 5 is a block diagram of an exemplary control system that may be used with compression system shown at FIG. 1, in which alternative control operations performed by the control system are illustrated; and

FIG. 6 is a compressor map of a prior art compression system.

Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of the disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of the disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to systems and methods for operation of a compression system. The system generally includes a compressor and an antisurge controller coupled to the compressor. The antisurge controller may receive one or more state measurements associated with the compressor, such as one or more thermodynamic state measurements, and calculates an operational point distance to surge for operation of the compressor in proximity to a surge line associated with the compressor. Thus, the system can facilitate operation of the compressor over a portion of a performance curve associated with the compressor, such that the compressor operates closer to a surge limit. Accordingly, accurate detection of these events, such as a surge, and protection from such events based on the detection may facilitate extending the life and increase intervals between outages of the compression equipment and associated processes.

Although the systems and methods disclosed herein may be described with respect to one or more power measurements and power calculations, those or skill will appreciate that the same calculations may be performed as a function of electrical current. In particular, the relationship, in general, of power to current can be given by the equation P=√3*V*I*cos φ, where P=power, V=voltage, I=current, and cos φ=power factor. Thus, the calculations described herein may be performed with respect to power, voltage, and/or current.

FIG. 1 is a block diagram of an exemplary compression system 10. In the exemplary embodiment, compression system 10 includes a compressor 12, such as a centrifugal, industrial centrifugal, or axial compressor. Compressor 12 operates to compress a fluid, such as, for example, a gas from a source (e.g., a gas pipeline) that is received via an inlet pipe 14. The compressed fluid is output from compressor 12 via a discharge pipe 16 for further processing or other usage.

Compression system 10 may use a recycle or blowoff valve 18 as well as associated pipes 20 and 22 for protecting compressor 12 from surge by recycling, or blowing off, all or part of flow from compressor 12. Such recycling or blowoff can be regulated by, for example, a control system 100 that selectively opens recycle or blowoff valve 18 to enable high pressure fluid received from pipe 20 to be transmitted to pipes 22 and/or 14 and thereafter into the suction side of compressor 12. In this manner, the pressure of the fluid in pipe 14 is adjusted prior to the fluid entering compressor 12, such that conditions conducive to surge are reduced or eliminated.

Compression system 10 can also include a drive shaft 43. In some embodiments, compression system 10 includes a thrust bearing 44 and one or more radial bearings 46 situated along drive shaft 43. Thrust bearing 44 may include one or more special pads, or discs, that may abut drive shaft 43. Thrust bearing 44 can be a rotary type bearing that permits the rotation of drive shaft 43 and that supports an axial load of drive shaft 43. Additionally, radial bearings 46 can enable rotational movement of drive shaft 43. However, unlike thrust bearing 44, radial bearings 46 may not be called upon to support the axial load of drive shaft 43, but rather, may support the weight of drive shaft 43.

As described above, recycle or blowoff valve 18 can be manipulated via control system 100. Control system 100 can provide antisurge protection for compressor 12. Control system 100 may also provide other control functions for compression system 10 (e.g. a turbomachinery train or unit) including compressor 12, its drive source 28, as well as other auxiliary equipment.

Control system 100 includes an antisurge controller 102 that monitors various parameters of compressor 12, such as various state and/or thermodynamic parameters and/or electric power and current parameters of compressor 12. Such parameters can be monitored, for example, by suction or inlet pressure measurements and discharge pressure measurements taken by one or more measurement devices or sensors. An example of these measurement devices is a suction or inlet pressure measurement device and a discharge pressure measurement device (described in greater detail below).

Antisurge controller 102 can also monitor thermodynamic parameters of compressor 12. These parameters are monitored, for example, by suction or inlet discharge temperature measurements taken by one or more measurement devices or sensors. These parameters are also monitored based upon flow measurements taken by a flow measurement device or sensor.

FIG. 2 is an exemplary compressor map 200 of compression system 10. As shown, a surge limit line 202, a surge control line 203 based on a 15% of surge safety margin, and a choke limit line 204 are defined. Exemplary compressor map 200 also illustrates a compressor operating point 206, a compressor performance curve 208, a region 210 that represents the operational safety margin, in which antisurge controller 102 may take one or more actions (e.g., opening recycle or blowoff valves 18) to avoid operation beyond surge limit line 202 and/or surge incidence. A region 212 is also shown. Region 212 represents the available safe operational envelope provided by antisurge controller 102 based upon the control operations described herein.

Surge limit line 202 defines the onset of surge in terms of compressor flow and compressor pressure or compressor head. Surge limit line 202 can further define the stable operating limit of compressor 12 in the low flow region. Thus, surge limit line 202 represents a flow limit whereby when the flow through compressor 12 decreases beyond this flow limit, operation of compressor 12 may become unstable. Surge control line 203 may define a safe distance to surge limit line 202. As compressor 12 approaches surge control line 203, antisurge controller 102 may open recycle or blowoff valve 18 to prevent compressor operating point 206 from crossing surge limit line 202. Similarly, choke limit line 204 defines the safe operating limit of compressor 12 in the high flow region.

FIG. 3 depicts and exemplary partial block diagram of compression system 10, in which control operations performed by control system 100 are illustrated. FIG. 4 is a flowchart illustrating an exemplary process 400 for use in determining an operational point distance to surge for compression system 10. For convenience, FIG. 3 and FIG. 4 are described in conjunction below.

Accordingly, in various embodiments, antisurge controller 102 is coupled to a plurality of sensors and/or transmitters, and acquires 402 from these sensors and/or transmitters at least one state measurement, such as at least one thermodynamic state measurement and/or at least one mechanical state measurement. The plurality of sensors and/or transmitters include, for example, a drive source current and/or power transmitter 302, a first inlet guided vane and/or variable geometry diffuser angle transmitter 304, a second inlet guided vane and/or variable geometry diffuser angle transmitter 306, a first pressure transmitter 308, a second pressure transmitter 310, a first temperature transmitter 312, and/or a second temperature transmitter 354.

First inlet guided vane and/or variable geometry diffuser angle transmitter 304 may be coupled to an inlet 314 of compressor 12, and second inlet guided vane and/or variable geometry diffuser angle transmitter 306 may be coupled to an outlet 316 of compressor 12. Similarly, first pressure transmitter 308 may be coupled to inlet 314 of compressor 12, and second pressure transmitter 310 may be coupled to outlet 316 of compressor 12. Likewise, first temperature transmitter 312 may be coupled to inlet 314 of compressor 12, and second temperature transmitter may be coupled to outlet 316 of compressor 12.

In the exemplary embodiment, drive source current and/or power transmitter 302 senses and transmits a drive source current and/or drive source power measurement 301 (or “PW”) indicating a power consumed by compressor 12, first inlet guided vane and/or variable geometry diffuser angle transmitter 304 senses and transmits an inlet guided vane and/or variable geometry diffuser angle inlet measurement 303 (or “Zs”), and second inlet guided vane and/or variable geometry diffuser angle transmitter 306 can sense and can transmit an inlet guided vane and/or variable geometry diffuser angle discharge measurement 305 (or “Zd”). Likewise, first pressure transmitter 308 can sense and can transmit an inlet pressure measurement 307 (or “Ps”), and second pressure transmitter 310 can sense and can transmit a discharge pressure measurement 309 (or “Pd”). Similarly, first temperature transmitter 312 can sense and can transmit an inlet temperature 311 (or “Ts”), and second temperature transmitter 354 can sense and can transmit a discharge temperature 313 (or “Td”).

As described elsewhere herein, antisurge controller 102 may multiply the drive source current and/or power measurement, PW, by the inlet temperature, Ts, and the product of this multiplication may be divided by the inlet pressure measurement, Ps to calculate 404 a corrected power 317 (“PWcor”). In other words, PWcor=PW*(Ts/Ps). Similarly, actual corrected current, Ccor, may be calculated according to the following equation: Ccor=A*(Ts/Ps).

Antisurge controller 102 may, in addition, divide the discharge pressure measurement, Pd, by the inlet pressure measurement, Ps, to calculate 406 a pressure ratio, 319 (“rp”). In other words, rp=Pd/Ps. The pressure ratio 319 may be provided as an input to a function 350 for calculating 408 the power 318 at the choke limit line 204 (“PW@CKLL”). Similarly, the pressure ratio 319 may be provided as an input to a function, 320, for calculating 410 a power 322 at the surge limit line 202, (“PW@SLL”). In various embodiments, function 320 and/or function 350 may be derived from one or more compressor performance maps (e.g., maps 200 and/or 600) and/or obtained by field surge and/or field choke testing. In addition, in various embodiments, function 320 and/or function 350 may be linear, polynomial (e.g., a first, second, or third degree polynomial), and/or piecewise.

Antisurge controller 102 may also calculate 412 a variable guided vane (“VGD”) modifier or modification factor 324 based upon a VGD modifier function 326, which may receive as an input the inlet guided vane and/or variable geometry diffuser angle discharge measurement 305 (or “Zd”). Similarly, antisurge controller 102 may calculate 414 an inlet guided vane (“IGV”) modifier or modification factor 328 based upon an IGV modifier function 330, which may receive as an input the inlet guided vane and/or variable geometry diffuser angle inlet measurement 303 (or “Zs”). In various embodiments, if there is no inlet guided vane and/or variable geometry diffuser angle discharge measurement 305, VGD modifier 324 may be equal to one. Likewise, if there is no inlet guided vane and/or variable geometry diffuser angle inlet measurement 303, IGV modifier 328 may be equal to one. In various embodiments, function 326 and/or function 330 may be derived from one or more compressor performance maps (e.g., maps 200 and/or 600) and/or obtained by field surge and/or field choke testing. In addition, in various embodiments, function 326 and/or function 330 may be linear, polynomial (e.g., a first, second, or third degree polynomial), and/or piecewise.

In various embodiments, antisurge controller 102 may multiply VGD modifier 324 by power 322 at the surge limit line 202, and the product of this calculation may be multiplied by IGV modifier 328 to provide or calculate 416 a modified power 332 at the surge limit line 202 (“PW MOD@SLL”).

Antisurge controller 102 may further subtract 418 power 318 at the choke limit line 204 from modified power 332 at the surge limit line 202 (e.g., PW MOD@SLL−PW@CKLL) to calculate an actual operational power 352 (or “Spam”). Antisurge controller 102 may also subtract 420 modified power 332 at the surge limit line 202 from corrected power 317 (e.g., PWcor−PW MOD@SLL) to calculate a surge margin 214 (as described above with reference to FIG. 2), and thereafter, calculate 422 an operational point distance to surge 334 for compressor 12 (“OPrel”) by taking the quotient as follows:

OPrel=1+[(PWcor−PW MOD@SLL)/(PW MOD@SLL−PW@CKLL)]

FIG. 5 is block diagram of control system 500, in which alternative or optional control operations performed by control system 100 are illustrated. The operations performed by control system 100 at FIG. 5 are identical to the operations performed by control system 100 at FIG. 3, except, as shown, that corrected power 317 may be calculated based upon the square root of compressor inlet temperature 311. For example, corrected power 317 may be calculated according to the following equation: Pwcor=PW*SQRT (Ts)/Ps. Similarly, actual corrected current, Ccor, may be calculated according to the following equation: Ccor=A*SQRT(Ts)/Ps.

Accordingly, antisurge controller 102 calculates operational point distance to surge 334 by calculating surge margin 214. More particularly, as described above, surge margin 214 is calculated by subtracting power 318 at the choke limit line 204 from modified power 332 at the surge limit line 202 (e.g., PW MOD@SLL−PW@CKLL). This same operation may be performed with respect to current (not shown) at the choke limit line 204 and modified current (not shown) at the surge limit line 202.

Further, as described above, antisurge controller 102 can calculate actual operational power 352 (or Spam) by subtracting modified power 332 at the surge limit line 202 from corrected power 317 (e.g., PWcor−PW MOD@SLL). Further still, in some embodiments, antisurge controller 102 calculates operational point distance to surge 334 relative to surge limit line 202 by taking the quotient as follows:

OPrel=1+[(PWcor−PW MOD@SLL)/(PW MOD@SLL−PW@CKLL)].

Thus, compressor 12 can be operable in conjunction with process 400, such that region 212 is relatively large in comparison to region 210. In other words, compressor 12 is operable in conjunction with process 400 along a majority of performance curve 208, which permits operation of compressor 12 within a large region 212. For example, as a result of the ability of compressor 12 to operate within a larger region 212, it may not be necessary to open recycle or blowoff valve 18 until compressor 12 begins to closely approach surge limit line 202. In addition, and as described above with respect to FIG. 1, opening of recycle or blowoff valve 18 can be regulated by antisurge controller 102, such that high pressure fluid received from pipe 20 is transmitted to pipes 22 and/or pipes 14 and thereafter into the suction side of compressor 12. As a result, the pressure of fluid in pipe 14 is adjusted prior to the fluid entering compressor 12, such that conditions conducive to surge are reduced or eliminated.

FIG. 6 is an exemplary compressor map 600 of a prior art compression antisurge system (not shown). Like compressor map 200, compressor map 600 shows a surge limit line 602, a surge control line 603 based on an operational safety margin of 10%, a choke limit line 604, a compressor operating point 606, a compressor performance curve 608, and a region 610 that represents the operational safety margin of 10%. As shown, antisurge controller 102 may take one or more actions, such as opening recycle or blowoff valves 18 to avoid operation beyond surge limit line 602 and/or surge incidence. A region 612 is also shown. Region 612 represents the available safe operational envelope provided by antisurge controller 102 based upon the control operations implemented by the prior art antisurge system. Unlike compressor map 200, operational point calculations in this prior art system are exclusively based on surge limit line 602 as a reference. Therefore, the surge control line 603 and operational safety margin (as represented by region 610) are made with reference to surge limit line 602 only. In comparison with compressor map 200, the available safe operational envelope 612, based on a 10% safety margin, illustrated at compressor map 600 is much reduced. In other words, a compressor operating in conjunction with a prior art surge protection process requires a large portion of performance curve 608 be removed from the safe or acceptable region of operation 612, and demands compressor blowoff valve 18 actuation through a much larger portion of performance curve 608.

Embodiments of the compression system, as described above, can facilitate operation of a compressor over a large portion of a performance curve associated with the compressor, such that the compressor operates closer to a surge limit. The system generally can include a compressor and an antisurge controller coupled to the compressor. The antisurge controller can receive one or more state measurements associated with the compressor, such as one or more thermodynamic state measurements, and calculates an operational point distance to surge for operation of the compressor in proximity to the surge line.

Exemplary technical effects of the compression system described herein can include, for example: (a) calculation of an operational point distance to surge based upon one or more state measurements associated with a compressor of the compression system; (b) operation of the compressor over a large portion of a performance curve of the compressor; and/or (c) operation of the compressor close to a surge line associated with the compressor.

Exemplary embodiments of a compression system and related components are described above in detail. The system is not limited to the specific embodiments described herein, but rather, components of systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. For example, the configuration of components described herein may also be used in combination with other processes, and is not limited to practice with the systems and related methods as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many applications where compressing a fluid is desired.

In description provided within this specification and the claims, reference is made to a number of terms, which are defined to have the following meanings.

The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about” and “substantially”, are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.

As used herein, the terms “processor” and “computer” and related terms, e.g., “processing device” and “computing device”, are not limited to just those integrated circuits referred to in the art as a computer, but broadly refers to a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits, and these terms are used interchangeably herein. In the embodiments described herein, memory includes, but is not limited to, a computer-readable medium, such as a random access memory (RAM), and a computer-readable non-volatile medium, such as flash memory. Alternatively, a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), and/or a digital versatile disc (DVD) may also be used. Also, in the embodiments described herein, additional input channels may be, but are not limited to, computer peripherals associated with a user interface such as a mouse and a keyboard. Alternatively, other computer peripherals may also be used that may include, for example, but not be limited to, a scanner. Furthermore, in the exemplary embodiment, additional output channels may include, but not be limited to, a user interface monitor.

Further, as used herein, the terms “software” and “firmware” are interchangeable, and include any computer program stored in memory for execution by personal computers, workstations, clients and servers.

As used herein, the term “non-transitory computer-readable media” is intended to be representative of any tangible computer-based device implemented in any method or technology for short-term and long-term storage of information, such as, computer-readable instructions, data structures, program modules and sub-modules, or other data in any device. Therefore, the methods described herein may be encoded as executable instructions embodied in a tangible, non-transitory, computer readable medium, including, without limitation, a storage device and/or a memory device. Such instructions, when executed by a processor, cause the processor to perform at least a portion of the methods described herein. Moreover, as used herein, the term “non-transitory computer-readable media” includes all tangible, computer-readable media, including, without limitation, non-transitory computer storage devices, including, without limitation, volatile and nonvolatile media, and removable and non-removable media such as a firmware, physical and virtual storage, CD-ROMs, DVDs, and any other digital source such as a network or the Internet, as well as yet to be developed digital means, with the sole exception being a transitory, propagating signal.

The techniques described herein can be implemented using one or more modules. As used herein, the term “module” refers to computing software, firmware, hardware, and/or various combinations thereof. At a minimum, however, modules are not to be interpreted as software that is not implemented on hardware, firmware, or recorded on a non-transitory processor readable recordable storage medium (i.e., modules are not software per se). Indeed “module” is to be interpreted to always include at least some physical, non-transitory hardware such as a part of a processor or computer. Two different modules can share the same physical hardware (e.g., two different modules can use the same processor and network interface). The modules described herein can be combined, integrated, separated, and/or duplicated to support various applications. Also, a function described herein as being performed at a particular module can be performed at one or more other modules and/or by one or more other devices instead of or in addition to the function performed at the particular module. Further, the modules can be implemented across multiple devices and/or other components local or remote to one another. Additionally, the modules can be moved from one device and added to another device, and/or can be included in both devices.

Although specific features of various embodiments of the present disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the present disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.

This written description uses examples to disclose the embodiments of the present disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the embodiments described herein is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 

What is claimed is:
 1. A method for operating a compression system, said method comprising: determining, by a controller, at least one of an operational point distance to surge and a surge margin based upon: at least one of an electrical power consumed by a compressor and an electrical current consumed by the compressor, and at least one thermodynamic state measurement associated with the compressor.
 2. The method of claim 1, wherein the at least one thermodynamic state measurement includes at least one of an inlet pressure at a compressor inlet and an inlet temperature at the compressor inlet.
 3. The method of claim 1 further comprising calculating, by the controller, a corrected power based upon the electrical power consumed by the compressor, an inlet temperature of the compressor, and an inlet pressure of the compressor.
 4. The method of claim 1 further comprising calculating, by the controller, a power at a surge limit line and a power at a choke limit line based upon the at least one thermodynamic state measurement.
 5. The method of claim 4 further comprising multiplying, by the controller, the power at the surge limit line by at least one of a variable guided vane modification factor and an inlet guided vane modification factor to generate a modified power at the surge limit line.
 6. The method of claim 5 further comprising: calculating, by the controller, a corrected power based upon the electrical power consumed by the compressor, an inlet temperature of the compressor, and an inlet pressure of the compressor; and calculating, by the controller, the operational point distance to surge based upon the modified power at a surge limit line and the corrected power.
 7. The method of claim 6 further comprising calculating, by the controller, the operational point distance to surge based upon a power at the choke limit line.
 8. A compression system comprising: a compressor including an inlet; a controller coupled to said compressor, said controller configured to: determine at least one of an operational point distance to surge and a surge margin based upon: at least one of an electrical power consumed by said compressor and an electrical current consumed by said compressor, and at least one thermodynamic state measurement associated with said compressor.
 9. The compression system of claim 8, wherein the at least one thermodynamic state measurement includes at least one of an inlet pressure at said compressor inlet and an inlet temperature at said compressor inlet.
 10. The compression system of claim 8, wherein said controller is further configured to calculate a corrected power based upon the electrical power consumed by said compressor, an inlet temperature of said compressor, and an inlet pressure of said compressor.
 11. The compression system of claim 8, wherein said controller is further configured to calculate a power at a surge limit line and a power at a choke limit line based upon the at least one thermodynamic state measurement.
 12. The compression system of claim 11, wherein said controller is further configured to multiply the power at the surge limit line by at least one of a variable guided vane modification factor and an inlet guided vane modification factor to generate a modified power at the surge limit line.
 13. The compression system of claim 12, wherein said controller is further configured to: calculate a corrected power based upon the electrical power consumed by said compressor, an inlet temperature of said compressor, and an inlet pressure of said compressor; and calculate the operational point distance to surge based upon the modified power at a surge limit line and the corrected power.
 14. The compression system of claim 13, wherein said controller is further configured to calculate the operational point distance to surge based upon a power at the choke limit line.
 15. An article of manufacture comprising a non-transitory, tangible, computer readable storage medium having instructions stored thereon that, in response to execution by a controller, cause the controller to perform operations comprising: determining, by the controller, at least one of an operational point distance to surge and a surge margin based upon: at least one of an electrical power consumed by a compressor and an electrical current consumed by the compressor, and at least one thermodynamic state measurement associated with the compressor.
 16. The article of claim 15, wherein the at least one thermodynamic state measurement includes at least one an inlet pressure at a compressor inlet and an inlet temperature at the compressor inlet.
 17. The article of claim 15 further comprising calculating, by the controller, a corrected power based upon the electrical power consumed by the compressor, an inlet temperature of the compressor, and an inlet pressure of the compressor.
 18. The article of claim 15 further comprising calculating, by the controller, a power at a surge limit line and a power at a choke limit line based upon the at least one thermodynamic state measurement.
 19. The article of claim 18 further comprising multiplying, by the controller, the power at the surge limit line by at least one of a variable guided vane modification factor and an inlet guided vane modification factor to generate a modified power at the surge limit line.
 20. The article of claim 19 further comprising: calculating, by the controller, a corrected power based upon the electrical power consumed by the compressor, an inlet temperature of the compressor, and an inlet pressure of the compressor; and calculating, by the controller, the operational point distance to surge based upon the modified power at a surge limit line and the corrected power. 